Is that a continuous measured current into the battery under all conditions? It's the right level of current to charge the battery when it's been discharged, but too much to maintain as a continuous current when the battery is full.
The regulator should be reducing the current considerably under full charge conditions, with very little going into the battery and only supplying enough current to replace any equipment load.
Going back to the original post, you say that 'the old dynamo has been replaced by a new alternator' and I'm wondering if the combination of the new alternator and the voltage regulator are just pushing too much charge into the battery. Is the regulator adjustable?